The present invention pertains to the radio communication art and, more particularly, to an antenna array coupling network.
Antenna systems wherein a single antenna structure is adapted to both transmit and receive radio frequency signals are well known in the communication art. Commonly, in applications wherein both transmit and receive operation occurs simultaneously, either duplexers or dedicated antennas or combinations thereof are used. That is, one or more antennas is dedicated to the transmit function whereas the remaining antennas perform a receive only function.
Recently, the need has arisen for an antenna coupling system which is capable of simultaneously utilizing a multi-sectored antenna array for both directive receive and omni-directional transmit functions. The basic array and its corresponding switching logic are described more fully in copending U.S. patent applications entitled "Sectored Antenna Receiving System", the first being invented by Timothy Craig and James Stimple, filed May 2, 1977 with Ser. No. 792,961, now abandoned and the second, invented by Timothy Craig, James Stimple and Paul Erickson, also filed May 2, 1977 with Ser. No. 792,963, now U.S. Pat. No. 4,101,836. In these systems, an antenna switch which is controlled by scan control logic sequentially couples selective antenna sectors to a receiver. The antennas are arranged in a configuration of individual sectored segments to cover a full 360.degree. of the horizontal plane. Once a transmitter signal is detected, the system activates to further modes to thereby lock onto that sector receiving the best signals from the transmitter.
It is desirable to expand the above described system so that it may both transmit and receive over the same antenna array. If possible, the simultaneous transmission of multiple transmitters is desired. Of necessity, it is imperative that signals transmitted by the array do not adversely effect the arrays receiving and scanning operation. Thus, isolation between the transmitted and received signals must be provided.